The response of animals to herbicide-induced habitat changes PublicDeposited

Descriptions

The objectives of this investigation were to examine the changes in vegetation resulting from application of herbicides, and to study the effects of these vegetative changes on the abundance and composition of small-mammal populations, and on deer usage of treated and untreated plots. Three areas in western Oregon were selected for study and half of each was treated with a combination of herbicides designed to control grasses and forbs without injuring Douglas-fir (Pseudotsuga menziesii (Mirb. ) franco). The effects of herbicide treatment were to eliminate or suppress grasses, control forbs, and to promote growth of shrubs and trees. Small mammals primarily associated with grass or meadow habitats decreased in abundance. The Oregon vole (Microtus oregoni) was the species most affected by the reduction in grassy vegetation. Species that find optimum habitat in brushy areas increased in abundance on treated plots. The deer mouse (Peromyscus
maniculatus) was the most common species to demonstrate a positive response on treated plots. The community response depended on the relative species composition. Deer activity, as measured by pellet-group counts, was greater on treated plots during the growing seasons. No significant differences were found in the occurrence of browsing as a result of herbicide-induced habitat changes. Browsing was influenced by season. Herbicide treatments improved deer habitat during the growing season without significantly increasing the browsing of Douglas-fir seedlings.